The present invention relates to reservoirs, and more particularly, to fluid reservoirs for use in gas turbine engines.
In many gas turbine engines, a fluid reservoir is used to store liquid lubricating oil for engine components. A supply pump attached to a supply passage takes liquid from the fluid reservoir to the engine components, and a scavenge pump attached to a scavenge passage returns the liquid from the engine components to the fluid reservoir. When a scavenge pump returns liquid to the fluid reservoir, it typically returns air along with the liquid. Consequentially, the fluid reservoir holds air and liquid. During normal operating conditions, the liquid settles at the bottom of the fluid reservoir and displaces air to the top. However, a fluid reservoir for a gas turbine engine mounted on an aircraft may experience “negative gravity” conditions such as the aircraft turning upside down, the aircraft accelerating toward the Earth at a rate equal to or greater than the rate of gravity, or the aircraft decelerating at the end of a vertical ascent. Under negative gravity conditions, the liquid in the fluid reservoir can rise to the top, which can expose the opening of the supply passage to air and interrupt the supply of liquid to the engine components. Certain engine components, such as gears and bearings, can be damaged in a relatively short period of time without lubrication.
Typically, a lubrication system includes a single fluid reservoir and a single supply pump driven by a high pressure spool. When the high pressure spool stops rotating or rotates at a reduced rpm (revolutions per minute), the single supply pump will ordinarily provide little or no liquid to engine components. Certain engine components can continue rotating when the high pressure spool stops rotating or rotates at a reduced rpm (revolutions per minute). For example, while the aircraft is parked on the ground or during an in-flight engine shutdown, wind may rotate a fan, a low pressure compressor, and, consequently, the low pressure spool and the corresponding gears and bearings. Certain gears and bearings could be damaged by non-lubricated operation.